Comparative physical and chemical studies of mitochondrial and supernatant malate dehydrogenase from pig heart are planned. Particular emphasis is to be made on studies of the structure-function relationship, particularly with respect to subunit interactions. Research will attempt to correlate anomalous kinetic behavior with the isomerization of intermediates in the catalytic mechanism. Also, the influence of ligand structure on isomerization rate will be investigated. Comparative chemical studies are planned of the primary structures of active site peptides.